An abradable material is known for ensuring dynamic sealing in a turbomachine, e.g., in a compressor of the axial-flow turbomachine. Such material is applied as a layer to an outer casing and is capable of eroding in the event of contact with the tips of rotor blades without damaging them. The mechanical integrity is preserved despite speeds of rotation of greater than 8000 rpm, and a relative speed between a blade tip and its seal substantially equal to the speed of sound. Such a material is also used for ensuring sealing under inner shrouds, or on a drive shaft bearing.
In this way, it is possible to design a compressor while reducing the operating clearance between the tips of rotor blades and the inner surface of the casing. The optimization can also take into account the expansion, the centrifugal force; and certain operating risks such as ingestions and pumping phenomena. An abradable material that forms a casing coating generally comprises aluminium, silica, polyester.
Document EP 1 010 861 A2 discloses a composition of a layer of abradable material for an axial-flow turbomachine compressor. The composition comprises a mixture of aluminium powder and silica powder, the aluminium being in the majority. In addition, the powder has a polymer powder with methyl methacrylate. This composition is applied by plasma spraying onto a wall of an axial-flow turbomachine compressor, the wall receiving beforehand a bonding layer with a majority amount of nickel, and aluminium in a lesser proportion. This composition makes it possible to produce an abradable seal with a requirement of corrosion resistance, however this corrosion resistance still warrants being improved in order to optimize the resistance and the efficiency of the turbomachine.